1. Field of the Invention
The present invention relates to a display device for effectively showing a front obstacle to a driver of an automotive vehicle.
2. Description of Related Art
A system for giving information about a front obstacle to a driver of an automotive vehicle has been put into market. For example, in a navigation system, an object irradiating infrared light is detected by an infrared camera mounted on a vehicle, and whether the object stays on a road or is crossing a road is determined. Further, whether the object is a pedestrian or another vehicle is detected. The image in front of the vehicle detected by the infrared camera is displayed on a display panel to the driver. However, a problem that a driver has to move his eyes onto the display panel from a windshield to get information displayed on the display panel is involved in this system.
To solve the above problem, a system is proposed in “HMI Transformed along with ITS Evolution” written by H. Asada et al., published in “Automotive Technology” (Page 73, Vol. 60, No. 2, 2006). In this system, a virtual image 105 in a shape of square surrounding a front obstacle 101 (such as a pedestrian) seen through a windshield 17 is shown on the windshield 17, as shown in FIG. 8 attached hereto. The image is formed in an on-board device and reflected on the windshield to show it as a virtual image to a driver. In this manner, the driver easily recognizes the front obstacle surrounded by the square virtual image 105 without moving his eyes from the front obstacle seen through the windshield.
A degree of collision danger with a front obstacle widely varies according to situations. For example, the degree of danger depends on a distance and a relative speed between the own vehicle and a front obstacle. In the system shown in the above publication, however, the virtual image surrounding the front obstacle does not vary depending on the degree of collision danger. That is, the same virtual image square is shown. Therefore, the driver is not able to quickly notice an obstacle having a high degree of collision danger. In addition, the virtual image 105 reflected on the windshield 17 vibrates according to vibration of the vehicle. As shown in FIG. 9 attached hereto, a virtual image 105a is shown at time T, a virtual image 105b at time T+1, a virtual image 105c at time T+2, and so on. That is, the virtual image 105 does not stay at the same position. Therefore, it is troublesome and uncomfortable for the driver to watch the virtual image 105.